Power injectors are devices used to inject fluids at controlled or programmed rates or pressures into patients. Important uses include computed tomography (CT) and angiography, where a radiopaque contrast medium is injected into a patient's vascular system to enhance diagnostic images. With power injectors, a motor-driven ram advances the plunger of a syringe under microprocessor control to provide control of injection parameters such as flow rate, volume and timing. Such injectors are often loaded with sterile empty syringes with their plungers forward and that are filled by drawing fluid from a supply into the syringe through the syringe nozzle by using the ram to draw the syringe plunger backward. In other situations, the injectors are loaded with prefilled syringes. In either case, the syringes used are typically disposed of after a single use.
A variety of syringes have been developed and are in use as both prefilled and fillable syringes. Some such syringes are provided with pushrods extending rearwardly from the plunger and beyond the rearward end of the syringe body. Reasons for this may include the need to operate the syringe plungers by hand, where the plunger pushrod serves as a handle for the manual advance or retraction of the plunger, or may include a desire to couple the plunger to a drive ram at a point outside of the syringe body, even where the syringe is empty and the plunger is at the forward end of the syringe. In such cases, the plungers may be permanently connected to the pushrods in manufacture or once assembled, and will project behind the rear rims of the syringe bodies.
Many of such syringes are further provided with an outwardly projecting flange which serves to hold or support the syringe against axial motion so that force can be applied between the flange and the remote end of the pushrod to operate the syringe plunger. The remote end of the pushrod is usually provided with a flat surface against which force can be applied to advance the plunger, as well as outwardly extending edge or rim structure that can be hooked and pulled to enable the plunger to be retracted. Such a pushrod may, for example, be provided with a disk shaped remote end that is larger in diameter than the pushrod shift. When inserted into holders of injectors or other syringe operating devices, such syringes are most conveniently configured to be loaded into the syringe holders of the devices from the side. Widely used syringes of this type include 100 ml. and 200 ml. syringes manufactured by Nemoto of Japan.
Certain of the inventors of the subject matter of the present application have provided front loading injectors that are adapted to receive front loadable syringes. A front loading injector is one in which a front loadable syringe is positioned in front of an opening in an injector holder and loaded into the holder by translating the syringe rearwardly, back end first, into the injector. Such a front loading injector is described and illustrated in U.S. Pat. No. 5,279,569, which is assigned to the assignee of the present application, and is expressly incorporated by reference herein.
In addition, breach loading or rear loading injector holders are still provided for many applications. Rear loading injectors are injectors in which a rear loadable syringe is positioned behind a holder of the injector and translated, so structure on the syringe, usually a flange or other outwardly extending element at the syringe rear, seats forwardly against the holder. Usually the holder opens for loading or unloading of a syringe by pivoting away from the injector housing, either in hinged or turret fashion. One such injector is described and illustrated in U.S. Pat. No. 4,695,271, which is assigned to the assignee of the present application, and is expressly incorporated by reference herein.
Both rear and front loading power injectors are provided with rams that extend into the rear of a body of a syringe supported in the holder of the injector. The rams have coupling elements on the front ends thereof that engage structure on the rear of the plunger, within the body of the injector, often in such a way that the plunger can be both advanced and retracted by the motion of the ram. Where empty syringes are used and filled after loading on the injector, the rams of many front and rear loading injectors are of a diameter somewhat smaller than the internal diameter of the syringe, which minimizes the risk that the ram will contact the inside of the syringe body and contaminate the cavity before the plunger is retracted to fill the syringe.
With syringes that have plunger pushrods or rearward plunger extensions, their use with either rear loading or front loading injectors is difficult to achieve. Such syringes are not compatible with the ram-plunger coupling structure with which front and rear loading injectors are provided and the extension of the pushrod rearwardly of the back end of the syringe body interferes with a support of the syringe in a suitable position on the syringe holder of the injector. Such coupling structure often includes a button or key at the center of the rear wall of the plunger with a mating socket or set of jaws centered on the tip of the ram. Furthermore, providing special purpose injectors configured to handle side loadable syringes has not been regarded as practical in the prior art.
Accordingly, there is a need for a power injector that can make use of pushrod type syringes, particularly prefilled syringes, and particularly for injectors that can also be used with syringes of the front and rear loadable types.